During the past 200 years, one-third of the CO2 from human activities is being taken up by the oceans, causing a rise in CO2 levels and a pH decrease ('ocean acidification'). An additional pH decrease is expected by 2100. These changes are expected to alter the secondary metabolism of primary producers and, consequently, the production of chemical anti-herbivory compounds. Herbivory play a key role in shaping community structure and functioning within seagrass meadows through the control of producers´ composition and abundance. Among marine producers, seagrasses are foundation species that facilitate whole communities by providing habitat and food to many herbivore species. To lessen herbivory impact, seagrasses may deploy chemical defences that reduce their quality as food. This seagrass resistance to herbivory is expected to shift under elevated CO2 levels and ocean acidification.
Currently most studies of ocean acidification involve short-term experiments, while areas with naturally high CO2 from volcanic vents can be exploited to investigate long-term effects of future ocean acidification on seagrass resistance against herbivores. In this project, we will compare the chemical defences against herbivores in control and CO2-enriched sites within seagrass meadows under natural CO2 gradients from volcanic vents in the Vulcano Island (Italy). Our results will provide valuable insights for understanding the ecological consequences of future impacts of ocean acidification on seagrass ecosystems.